Greg Zyla: Chevelle SS 396 is really a 402 SS

Greg Zyla

Monday

Jan 24, 2011 at 12:01 AMJan 24, 2011 at 1:57 AM

Q: I know that in 1970, the SS 396 isn't really an SS 396 in that it came with a 402-inch V8 engine. How did this happen and why wasn't the car called an SS 402, like the SS 454 Chevelles that year? I've always loved those big-block Chevy engines.

Q: Greg, I really like the old car columns and seek your knowledge. I know that in 1970, the SS 396 isn't really an SS 396 in that it came with a 402-inch V8 engine. How did this happen and why wasn't the car called an SS 402, like the SS 454 Chevelles that year? I've always loved those big-block Chevy engines. Matt L., e-mail from Massachusetts.

A: Matt, I, too, love the big-block Chevys, and the history of the motor is interesting.

As for your question, in 1970 all "SS 396" Chevelles came standard with a 402-inch big block, as Chevy bored the engine .030-over from 4.09 to 4.13 piston size. However, for marketing purposes, Chevy wisely decided to keep the SS 396 moniker after the introduction of the rare 1965 Chevelle SS 396 and its subsequent popularity with the muscle-car crowd through 1972.

Frankly, "SS 402" just didn't have the "right sound," although "SS 454" did.

Here's another fact on Chevy big-blocks. Although the 402 was a regular - albeit not promoted - big-block production engine, many people don't know that Chevrolet actually built five big-block engines in addition to the popular 396-427-454 engines. These include the 402 that we speak of and a 366-incher used in medium-duty trucks and school buses.

Additionally, all of the big blocks, except for the 454, relied on a 3.76-inch stroke crankshaft, which was internally balanced. The 454, meanwhile, came with a 4-inch stroke crank and relied on an externally balanced setup, which included a specially weighted flywheel and torsional damper.

The modern-day big-block engine debuted under great secrecy at the Daytona 500 in 1963 as the "Mark IV Mystery Motor," and was used by racers like Junior Johnson, Rex White and Johnny Rutherford. The Mystery Motor, with it much better breathing cylinder heads, replaced Chevy's first big-block effort, namely the "W style" 348-409-427 engines, the latter used in drag racing as a 427 Z-11 option in 1963 only.

The 1963 Mark IV Mystery Motor big block used at Daytona didn't come into mass production until 1965 in the Chevelle SS and Corvette as a 396 engine producing 375 horsepower. Today, the '65 Chevelle SS 396, known as a Z16 option, is one of the collector enthusiast’s top holdings, as just 201 were ever produced.